1. Field of the Invention
The present invention is generally related to a cooling system for a marine engine and, more particularly, to a closed cooling system in which coolant is recirculated through heat emitting portions of the marine engine and particularly through exhaust components such as an exhaust manifold and elbow.
2. Description of the Related Art
Those skilled in the art of marine engine cooling systems are familiar with many types of systems that circulate coolant in thermal communication with heat emitting components. Some cooling systems are open loop systems in which water is drawn from a body of water, passed through conduits in thermal communication with the heat emitting portions of the propulsion system, and then returned to the body of water. Some systems are closed cooling systems in which a coolant, such as an ethylene glycol mixture, is recirculated through conduits disposed in thermal communication with heat emitting components of the propulsion system. Typically water is drawn from a body of water in which the marine propulsion system is operated and the water is caused to flow in thermal communication with the coolant of the closed loop portion of the system. In these types of marine propulsion systems, some heat emitting components are cooled by the coolant within the closed loop portion of the system and other components are cooled by the water drawn from the body of water. The closed loop coolant is cooled by flowing in thermal communication with the water from the body of water as the two fluids flow through a heat exchanger.
U.S. Pat. No. 4,220,121 which issued to Maggiorana on Sep. 2, 1980, discloses a heat exchanger for marine propulsion engines. The heat exchanger is provided for a pressurized, closed cooling system for a marine propulsion engine. The heat exchanger includes a closed spiral passageway means for fresh cooling water drawn from the lake or other water body. An outer housing encloses the spiral passageway and includes baffle means for directing of a coolant in a spiral path over the cooling passageway means within the housing. The coolant is thereby cooled by the circulating cold freshwater. An air discharge passageway means is provided in the center of the spiral path. The centrifugal forces associated with the spiral flow of the cooling coolant results in the water moving outwardly within the passageway while the air tends to collect within the center thereof where it is collected and discharged by the air passageway means for automatic separation and removal of the air.
U.S. Pat. No. 4,991,546, which issued to Yoshimura on Feb. 12, 1991, describes a cooling device for a boat engine. A cooling jacket delivers its coolant to an exhaust manifold cooling jacket adjacent the inlet end of the exhaust manifold and coolant is delivered from the exhaust manifold cooling jacket to a further cooling jacket around the inlet portion of an exhaust elbow. In one embodiment, a closed cooling system is provided for the engine cooling jacket, exhaust manifold cooling jacket and the elbow cooling jacket. In another embodiment, the system discharges coolant back to the body of water in which the watercraft is operating through a further cooling jacket of the exhaust elbow that communicates with its discharge ends.
U.S. Pat. No. 5,004,042, which issued to McMorries et al. on Apr. 2, 1991, discloses a closed loop cooling system for a marine engine. The closed loop cooling system includes a marine engine having a cooling fluid passage defined therethrough through which a cooling fluid stream may pass. A shell and tube heat exchanger has a tube side flow path and a shell side flow path defined therein. Cooling fluid conduits connect the cooling fluid passage from the marine engine to the tube side flow path so that the cooling fluid stream from the engine is directed through the tube side flow path of the heat exchanger. A raw water supply system directs a raw water stream from a body of water through the shell side flow path and then back to the body of water. The heat exchanger includes an outer housing and a tube bundle receiver in the outer housing.
U.S. Pat. No. 5,746,270, which issued to Schroeder et al. on May 5, 1998, discloses a heat exchanger for a marine engine cooling system. The assembly is provided for a marine propulsion system having a closed loop cooling system. The heat exchanger body encloses a series of tubes carrying sea water which removes heat from the engine coolant. The heat exchanger includes an integrally connected top tank. A single venting orifice is provided into the top tank from the heat exchanger body. A heat exchanger coolant outlet is in direct fluid communication with both a system bypass and the coolant in the top tank. An auxiliary inlet for coolant from the top tank is located in the heat exchanger coolant outlet downstream of the bypass inlet, thereby promoting the ability of the system to draw coolant through the top tank rather than the bypass. The construction minimizes cavitation and reduces the creation of negative pressure at the circulating pump.
U.S. Pat. No. 6,368,169, which issued to Jaeger on Apr. 9, 2002, discloses a marine engine cooling system with siphon inhibiting device. A siphon inhibiting valve is provided for a marine engine cooling system. The purpose of the valve is to prevent the draining of the pump and outboard drive unit from creating a siphon effect that draws water from portions of the cooling system where heat producing components exist. The valve also allows intentional draining of the system when the vessel operator desires to accomplish this function. The valve incorporates a ball that is captivated within a cavity. If the ball is lighter than water, its buoyancy assists in the operation of the valve.
U.S. Pat. No. 6,748,906, which issued to White et al. on Jun. 15, 2004, discloses a heat exchanger assembly for a marine engine. It is disposed between first and second sides of a V-shaped engine configuration. A plurality of tubes and related structure are disposed within a cavity formed as an integral part of an air intake manifold of the engine. A first cooling fluid, such as ethylene glycol, is circulated in thermal communication with outer surfaces of the plurality of tubes within the heat exchanger and a second fluid such as lake or sea water is circulated through the internal passages of the plurality of tubes. A conduit is provided within an end portion of the heat exchanger to remove heat from a lubricant, such as oil, of the internal combustion engine.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a marine propulsion system could be provided with a cooling system that cools not only engine components, but exhaust components, with the coolant of the closed loop portion of the system. The components which are cooled by the closed loop coolant could then be manufactured from a low density metal, such as aluminum, that would otherwise be prohibited if they were exposed to water drawn from a body of water in which the marine propulsion system is operated.